Good points. All the same, I still think that quilted armor must have been used. Something much like it must have been worn under ring-armor, and its protective qualities would have been obvious. The cost of equipping large numbers of men, particularly during the financally-strapped late Empire when many of them, such as limitanei, defended the border in forts or from the walls of cities and seldom fought in pitched batttles argues strongly for the use of cheap but adequate protection.
Best regards!
Erik
https://www.erikhildinger.com